The present invention relates to marking devices, particularly rotary head markers for imprinting a moving work piece such as a strip of bag material or the like which permits a fresh inking roller to be inserted without stopping the printing operation.
Rotary head printers are employed for imprinting information on a work piece such as bag material in strip form and the like. A common type of such rotary head printers has a rotatably driven head carrying printing in the form of type bars with the type exposed at the circumference of the print head for successively contacting an inking roll and the work piece, which is moved between the driven head or printing roll and a backing roll. Such marking units may be utilized in association with a packaging or filling machine, or may be employed to imprint film or similar material which is then wound onto a roll for subsequent use. This type of marker or printer is used to print small or selected areas of preprinted film panels in the form of a film strip consisting of a longitudinally extending series of such panels, which will subsequently be cut to form the individual faces of bags or packages.
It is necessary to change the type carried by the print head with some frequency for different imprinting runs. It is also necessary from time to time to vary the size or the transverse location of the imprinting, or the spacing of the imprints along the length of the work piece. It is also necessary to frequently change the inking roller which contacts the type face at least once per revolution of the printer roller so as to supply a fresh coat of ink to the type face. Such rollers must be changed, for example, due to wear or for changing ink colors or to replenish the ink supply.
A rotary print head is disclosed in the co-pending application of Charles F. Davison, Ser. No. 535,997 filed Sept. 26, 1983. The apparatus disclosed therein provides, among other structural features and advantages, means for easily removing and retaining one or more type holders in the printer roll, means for adjusting the positions of various rolls for accommodating rolls of different sizes, and means for easily removing and replacing the ink roller. This apparatus, however, employs only a single inking roller and therefore operation of the printing unit must cease whenever an inking roller is to be removed and replaced. In many applications, such removal and replacement of the inking roller must be undertaken several times a day, such as after a specified number of printing impressions.
It is therefore an object of the present invention to provide a marking apparatus which permits easy and rapid replacement of an inking roller without disrupting the printing operation.
The above object is inventively achieved in a marking apparatus having dual inking rollers carried on a common support member, the support member being movable so as to position one of the ink rollers in inking engagement with the printer roller, while simultaneously positioning the other ink roller out of engagement with the print roller so as to permit replacement of that roller while the other roller continues to operate in the printing sequence.
In one embodiment of the apparatus, the support member carrying the dual inking rollers is connected to a manually actuatable lever having an eccentric cam thereon which is movable in a slot in the support member. As the lever is moved through an arc, the eccentric cam is rotated within the confines of the slot, causing the support member to move to one side or the other in order to place one of the dual inking rollers in inking engagement with the printer roller, while simultaneously moving the other roller out of engagement for replacement thereof.
In another embodiment of the invention, the eccentric cam is carried on the pinion of a rack and pinion arrangement, the rack being movable by a hydraulic cylinder.
In another embodiment, the eccentric cam is carried on a gear or toothed wheel in engagement with a rotary air cylinder.
In all of the embodiments, the printer roll may be equipped with a counter for providing a signal, such as a visual signal, after a specified number of revolutions, and therefore a specified number of printing impressions, of the printer roller, thereby designating that the inking roller currently in engagement with the printer roller should be replaced. Upon observing this signal, a worker can either manually move the lever to effect engagement of the fresh inking roller, or can actuate suitable controls for effecting operation of the hydraulic cylinder or the rotary air cylinder to achieve the same result.
In a further embodiment of the invention, the non-manually actuatable embodiments, namely the embodiments employing the hydraulic cylinder and the rotary air cylinder, may be equipped with a control unit to which the counter is connected for automatically effecting a changeover to the fresh inking roller upon the occurrence of a specified number of revolutions of the printer roll. The control unit may, for example, actuate a solenoid-controlled valve connected to the hydraulic cylinder or the rotary air cylinder. Upon successive occurrences of the specified count, the valve is actuated so as to cause the support member to move in a direction opposite to the direction in which it was previously moved upon attainment of the previous count.